No engine limitations help make this the quickest and fastest doorslammer class in the world!


Purse for this class is $17,000/event and broken down as follows:

Winner: $6,000

Runner Up: $2,000

Semi: $1,000

Quarter: $750

Qualifier: $500

DESIGNATION:PX or Pro Extreme followed by car number. PM, Pro Mod or Pro Modified not allowed. Numbers must be at least 4” tall and on both side windows, upper left of rear window and upper right of windshield.

FIELD: 16 car qualified field.

MINIMUM WEIGHT: 2350 lbs with driver. No maximum Cubic Inch Limit. All rules subject to change at the sole discretion of the X-DRL Technical Services Department.


BODY APPEARANCE: All vehicles must be professionally finished, painted, lettered, numbered and decaled.

BODY: Funny car or one piece bodies not allowed even if equipped with doors. Maximum front end overhang of 45” as measured from centerline of front spindles. An X-DRL accepted extension may be used to create  45” overhang if the front end overhang of the originalbody is less than 45”. All bodies must originate from a documented production vehicle. All new cars must be accepted by the X-DRL Technical Services Department  prior to construction. If using any percentage of Nitromethane, the Inside of front end and hood must be painted with X-DRL accepted fire retardant paint on any vehicle using any percentage of nitromethane for fuel.

DOORS: Required. Doors must be functional and able to be opened from both the inside and outside of the vehicle. Doors may be fabricated from carbon fiber, fiberglass or metal. A metal deflector between the fenders and the leading edge of both doors is required.

FIREWALL: All firewalls must be made of steel or titanium (.024” minimum thickness). Carbon, Aluminum, Magnesium, ect. prohibited.

FLOORS: Replacing stock floors with .024″ steel or .032″ aluminum allowed (.032 on any vehicle using any percentage of nitromethane for fuel). Driver’s side floor pan must be .024″ steel (.032 on any vehicle using any percentage of nitromethane for fuel) and must extend from firewall to the back of the drivers seat and must be welded in place.Carbon fiber or composite materials may not be utilized in any portion of the flooring in the driver’s compartment except for any panel located behind the driver including suspension covers and wheel tubs.

HOOD SCOOP: One opening only. Must be finished and painted to follow the bodies paint scheme.

TAIL LIGHT: Functional rear tail light is required. Minimum 1 tail light required to be operational and controlled from the drivers compartment.

WINDOWS AND WINDSHIELD: .125” minimum polycarbonate materials, such as Lexan MR 4000 or equivalent required. Windows behind the drivers and passenger side windows may be replaced with Carbon Fiber or Fiberglass painted or decaled to simulate windows. An opening with a 4″ diameter minimum is required on side windows adjacent to the driver.


BATTERY: Maximum of two batteries allowed. All batteries must be securely sing metal fasteners. Must have an external master mechanical electrical disconnect at the rear of the vehicle marked “PUSH OFF”.

BRAKES: Four wheel brakes with dual master cylinder mounted above frame rails required.

CHASSIS: Must be SFI Spec 25.1E or 25.2 with current NHRA certification tag prior to competition.

DRIVER LOCATION: Must be in conventional left hand drive location.

GROUND CLEARANCE: Minimum of 3” required from front of car to 12” behind front axle centerline. 2” minimum for remainder of car.

STEERING: Stock type steering in conventional location required. Disconnect meeting SFI Spec 42.1required.

SUSPENSION: Race car type suspension required. Solid suspension prohibited. Minimum of 1 hydraulic shock absorber required on each wheel.

TIRES: Slicks permitted. Must be automotive type designed for racing. Tires cannot be extend outside of bodyline. All tires must have manufacturer, model and or part number and size information clearly and permanently designated on sidewall.

WHEEL BASE: Minimum 100″, Maximum 115″. Bodies derived from a Ranger, Dakota, or S-10 Maximum 125”. Maximum variation is 2” side to side.

WHEELIE BARS: Required, Must have non metallic wheels.

 WHEELS: Wheels meeting SFI Spec 15.1 required. Inner Liners accepted. Maximum rear wheel width 16” measured between the inner and outer tire mounting surfaces. Use of a liner mandatory on all non bead lock wheels.


CLUTCH/FLYWHEEL: Flywheel and clutch meeting SFI Spec .3, 1.4, or 1.5 certification required. SFI Spec 29.2 flexplate required on all torque converter equipped cars. Cars running any percentage of Nitromethane must use SFI Spec 1.3 Flywheel and Clutch assembly.

CYLINDER BORE SPACING: Maximum Bore Spacing is 5.300”.

DRIVELINE: A full 360 degree drive shaft tube is required over yoke, extended a minimum of 12” required from transmission tail shaft. Minimum thickness of tube housing is .050” chrome-moly or titanium. Two piece units accepted with a minimum of 6 attachment points using 3/8” grade 8 bolts. SFI Spec 43.1 driveshaft required.

ENGINE CONTAINMENT SYSTEM: SFI Spec 7.1 lower engine containment system required. If a flexible 7.1 system is utilized, it must be supported by a belly pan made from carbon fiber or .032” aluminum with a minimum 2” vertical lip.

ENGINE SETBACK: Maximum of 10% of total vehicle wheel base as measured from the centerline of the forward front spindle to center of front spark plug hole.

EXHAUST: Open conventional style headers required. Exhaust gasses must be directed out of the body and away from the driver and fuel system.

HARMONIC BALANCER: SFI Spec 18.1 certification required.

FLYWHEEL SHIELD: SFI Spec 6.3 certification required.

FUEL: Alcohol, gasoline, methanol and nitromethane allowed. The use of nitromethane in screw-type supercharged engine is prohibited. Maximum percentage of nitromethane allowed in centrifugal or roots-type supercharged engine is 50%. Maximum percentage of nitromethane allowed in a non forced induction injected fuel engine is 50%. Non Forced Induction Fuel injected entries must be accepted by X-DRL Technical Services Department prior to competition.

IGNITION: One spark plug per cylinder maximum allowed on all supercharged or turbocharged vehicles.

INTAKE MANIFOLD: SFI Spec 23.1 Burst Panel required.

NITROUS OXIDE: Allowed in vehicle using Alcohol or Gasoline, Prohibited on any vehicle with any percentage of nitromethane.

REAR END: Automotive type, Full-floater rear end required. Titanium and or Aluminum Wheel studs prohibited.

STARTER: Optional. No push starts allowed.

SUPERCHARGER AND OVERDRIVE: Use of any size centrifugal, roots-type or screw-type supercharger allowed. Maximum overdrive for a roots-type supercharger is 1.70 (70 percent over). Maximum overdrive for a PSI screw-type supercharger is 2.28 (128 percent over). Maximum overdrive for a Whipple screw-type supercharger is 1.60 (60 percent over). All screw-type superchargers must be certified to SFI Spec 34.1 Any new screw-type supercharger must be submitted and accepted to the X-DRL Technical Services Department prior to competing at an X-DRL event. All screw-type superchargers must display a current SFI certification tag to be eligible for use in competition.

TRANSMISSION: Any type allowed. All entries must utilize a one piece transmission shield meeting SFI Spec 4.1.

TURBOCHARGER: Any size allowed. All turbochargers must meet SFI Spec 61.1.


CREDENTIALS: A valid X-DRL membership X-DRL, NHRA, or IHRA Competition License is required to compete. Valid IHRA or NHRA competition licenses may be transferred when presented with a current physical.




TOW VEHICLES: Allowed. A valid driver’s license is required to operate any type of tow vehicle. All passengers must be seated inside of vehicle with all doors closed. Riding in open hatchback, trunk or cargo area not allowed. ATV’s are allowed with a maximum of one passenger who must be seated at all times. Golf carts are allowed with a maximum of three passengers who must be seated at all times. Posted pit speeds must be obeyed at all times. If pit speed is not posted, maximum pit speed will be 10 mph.


DRIVER RESTRAINT SYSTEM: SFI Spec 16.1 certification required. 7 point system recommended.

FIRE SYSTEM: SFI Spec 17.1 system required. System must contain a minimum of 20 lbs of fire suppression agent. One nozzle required inside driver’s compartment must be directed at driver’s feet. Two or more nozzles must be directed at front of engine and fuel cell. FIre suppression system must be released with a single actuation (i.e. single handle, button or lever).

HEAD AND NECK RESTRAINT: SFI Spec 38.1 required. An aluminum skid plate is recommended above driver’s head.

HELMET: SN-2000 or newer of SFI Spec 31.2 or 41.2 required. SA-2000, SA-2005 or 31.2A with a shield required when utilizing any percentage of nitromethane. Use of open face helmet prohibited. Eject Helmet Removal System (Part #SDR 890-01-30) or equivalent required.

MASTER ELECTRICAL CUTOFF: Required. Must be clearly labeled “PUSH OFF”.

PARACHUTES: Dual parachutes required. Separate shroud-line mounting points with 1/2” sleeved grade 8 bolts required.

PROTECTIVE CLOTHING: A driver’s suit meeting SFI Spec 3.2A/20, gloves meeting SFI Spec 3.3/20, shoes meeting SFI Spec. 3.3/20 and a head sock meeting SFI 3.3 required. A head sock is not required when a helmet manufactured with a skirt meeting SFI Spec 3.3 is used.

RF SHUTDOWN RECEIVER: Properly functioning Electrimotion shutoff device (PN: RF001PS or combination PN: SB001 and RF001) required.

ROLL BAR PADDING: SFI Spec 45.1 required.

SUPERCHARGER RESTRAINT: SFI Spec 14.2 minimum required on all roots-type superchargers. SFI 14.21 required on all screw-type superchargers. You must utilize the entire assembly including bag, plate and straps.

UPHOLSTERY: Driver’s seat foamed with energy absorbing material, formed for the driver and covered with flame retardant material is required. “Wrap Around” type seat or fiberglass/carbon fiber one-piece bucket accepted seat frame of chrome-moly tubing must be installed as a permanent part of the chassis. Lateral Helmet supports required.

WINDOW NET: SFI Spec 27.1 required.